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1
Perkins, Andrew Mark. "Magnetic studies of speleothems." Thesis, University of East Anglia, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359381.
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The Natural Remanent Magnetizations (NRMs) of rocks and sediments relate to past variations of the Earth's geomagnetic field (GMF). Studies of speleothems (cave deposits such as stalagmites) have shown that they often possess measurable NRMs. However, there have not been extensive studies of the magnetic minerals responsible for the NRM, nor in determining the type and origin of the NRM. A selection of speleothems has been studied by palaeomagnetic and rock magnetic techniques to identify the magnetic minerals within them and the carriers of the NRMs. Electron microscope studies of extracted magnetic phases provide suggestions as to their origin. These studies have been combined with observations of speleothem surfaces to address the question of how the NRM is acquired. The NRMs and magnetic mineralogies of most speleothems are dominated by magnetite, with hematite and goethite present as accessories. Some samples are dominated by hematite. The bulk magnetic content of most speleothems does not vary and consequently there is only a single primary component of magnetization. However, there are exceptions. Rock magnetic data suggest that interaction between magnetic phases may be occurring and thus these data cannot be interpreted unambiguously in terms of magnetic grain size. Electron microscope studies have shown that the techniques for extracting and preparing magnetic grains cannot be used on a quantitative basis. On a qualitative basis, however, detrital grains (<0.01μm to »1Oμm, composed of magnetite, hematite and titanomagnetite), hexagonal or cubic grains (<0.1μm, composed of magnetite) and needle-like grains (<2μm, possibly goethite) have been observed. A detrital remanent magnetization contributes to the NRM of speleothems and is probably more important than previously suggested. Detrital grains are introduced into speleothems either via floodwaters or through feedwaters. It is suggested that the NRM is acquired due to grains becoming trapped in depressions in the speleothem surface. Experiments suggest that, in the near-absence of oxygen, inorganic precipitation of magnetite could occur during speleothem growth. Iron-chelating organic compounds could also introduce iron into caves. Further work is needed on de-chelation mechanisms, the transport of detrital and organic material into caves, the thermodynamic behaviour of iron at low temperatures and the oxygen content of waters in and entering caves. The recent introduction of mass spectrometry for dating speleothems suggests that the reliability of speleothems as records of past behavioural features of the GMF could be assessed to a greater degree.
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Blyth, Alison. "Lipid biomarkers in speleothems." Thesis, University of Newcastle Upon Tyne, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435638.
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Sundqvist, Hanna S. "Speleothems as environmental recorders : A study of Holocene speleothems and their growth environments in Sweden." Doctoral thesis, Stockholm : Department of Physical Geography and Quaternary Geology, Stockholm University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-1408.
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Van, Beynen Philip Edward. "Investigations into the fluorescence of calcitic speleothems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0028/NQ51173.pdf.
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Van, Beynen Philip Edward. "Investigations into the fluorescence of calcitic speleothems /." *McMaster only, 1998.
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6
Serrato, Marks Gabriela. "Investigating Mexican paleoclimate with precisely dated speleothems." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129056.
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Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2020Cataloged from student-submitted PDF of thesis. "September 2020."
Includes bibliographical references.
Speleothems, or sedimentary rocks formed in caves, act as valuable archives of past climate change due to their suitability for U-series dating and high-resolution proxy analysis. These records can provide insights into water availability and controls on hydrology prior to the instrumental record. In this thesis, I present three records from newly-analyzed Mexican stalagmites using stable isotope (oxygen and carbon) and trace element to calcium (Mg/Ca and Sr/Ca) ratios as proxies for changing hydroclimate. Chapter 2 presents a precisely dated, mid- Holocene record of high rainfall and limited precipitation variability in the Yucatan Peninsula, Mexico. Chapters 3 and 4 present novel climate records from northeastern Mexico, an understudied region of North America. Both records come from cave sites within the Mexican arid zone, which is simultaneously experiencing increased water scarcity and a rapidly growing population. In Chapter 3, I examine a speleothem from the first millennium of the Common Era, which showed that there is a precipitation dipole between northern and southern Mexico. Chapter 4 highlights, for the first time at decadal resolution, the northeast Mexican response to the 8.2 ka event and the Younger Dryas. These chapters show that the San Luis Potosí region is vulnerable to droughts under multiple climate mean states, and is subject to drying as Atlantic Meridional Overturning Circulation weakens due to anthropogenic climate change. The climate records detailed in this thesis improve our understanding of controls on Mexican hydroclimate and can serve as benchmarks for climate models.
by Gabriela Serrato Marks.
Ph. D.
Ph.D. Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution)
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Österlin, Carl. "STABLE CARBON ISOTOPES IN SPELEOTHEMS FROM TEMPERATE AREAS." Thesis, Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-55353.
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Speleothems are considered a reliable proxy for paleoclimatic reconstructions and analysis of stable carbon isotopes in speleothems is used for paleoclimatic reconstructions. However, in temperate areas that lacks C4 vegetation there are uncertainties in how to interpret changes in the δ13C signal. The aim of this study is toincrease the understanding of how the δ13C signal in speleothems from temperateareas can be interpreted. The study was divided in two parts, first a literature studythat focused on interpretations of the δ13C signal in speleothems from temperate areasand a case study in which a comparison of seven 13C records from similarenvironments in the Scandes Mountains and the Alps are made. The results from the literature study were used in the case study to draw conclusions on tree line and vegetation changes during Holocene in central northern Scandinavia. The study showed that trends in interpretation of the δ13C signal in speleothems from temperateareas are that low δ13C values are interpreted as wetter, warmer conditions with higherbio productivity, and high δ13C values are interpreted as colder, drier conditions withlower bio productivity. Further it was found in the study that vegetation changes seen in Holocene pollen data are also seen in δ13C records from Scandinavia. The δ13Csignal in temperate speleothems therefore appears to be related to changes invegetation density and to tree-line changes.
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Mason, Jennifer. "Palaeoclimatic Records from Speleothems in the Eastern Mediterranean." Thesis, University of East Anglia, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520432.
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Speleothems are key archives of palaeoclimatic information, chronologies for which can be precisely derived by Uranium Series methods. This investigation uses stable isotopes, trace elements and petrography in speleothems from the Eastern Mediterranean to reconstruct palaeoclimatic parameters in the area over the last -100 ka. Speleothems were collected along a transect from North-East to South West Turkey to Greece. Five stalagmite samples were selected for detailed geochemical analysis which was anchored by - 30 Uranium-Series dates. Most notably, oxygen isotope ratios in a stalagmite from Karaca cave, northeast Turkey exhibit similar temporal patterns to the Greenland ice core oxygen isotope records and to Chinese speleothem records of East Asian Monsoon (EAM) fluctuations over the period 77 ka to 6 ka. Winter rainfall maxima in north-east Turkey coincide with periods of intensified EAM. The isotope curve is interpreted as an insolation (precession) forced record of rainfall seasonality on glacialinterglacial timescales, with periods of high Northern Hemisphere insolation giving rise to cool wet winters and hot dry summers. Millennial-scale variability is caused by shorter-term changes in seasonality of precipitation and/or switching of moisture source areas in response to the stadial-interstadial climatic oscillations originating in the North Atlantic Basin and widely recorded in both marine and terrestrial climate records. Oxygen isotope rations in a 21 ka to7 ka stalagmite from southern Greece are interpreted similarly to Karaca. Shifts in S13C values in the record are related to soil biogenic activity. An isotopic event at 21 ka is interpreted as a short term increase in winter rainfall in response to increased seasonality due to increased insolation (precession). In south-west Turkey the 110 ka to 68 ka KE- I record is characterised by several large shifts in &180 and 613C corresponding to MIS 4,5a, 5b and 5c. These variations are again related to changes in seasonality of rainfall and are correlative with the Hulu speleothem record and Greenland ice core oxygen isotope records.
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Hodge, Edward James. "Palaeoclimate of the western Mediterranean region : results from speleothems." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411111.
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Kaushal, Nikita. "High resolution paleo-monsoon records from peninsular Indian speleothems." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:ab1ca849-185f-4619-83d9-fffe48e5cd2b.
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The Indian Summer Monsoon is a major component of the global climatic system. Stalagmites have a proven ability to provide information of such monsoon systems. In this thesis, examination of cave records and field work provides a framework of the spatial and temporal distribution of stalagmites in peninsular India. Stable oxygen isotope records from stalagmites are supported by trace element records. An aragonite stalagmite from the west coast of India suggests that changes in growth surface can effect precipitation through time available for dissolved inorganic carbon removal. Calculation of empirical partition coefficients from the aragonite stalagmite indicates that U/Ca, Sr/Ca and P/Ca ratios may be paleo-aridity indicators through the process of Prior Aragonite Precipitation. There may also be source and/or temperature control on the partitioning of Sr/Ca into the aragonite stalagmite. These are the first trace element measurements for stalagmites from peninsular India and some of the few available from aragonite stalagmites. The δ18O composition of a calcite stalagmite from central India that grew from 3130 to 2100 years BP is consistent with the hypothesis that δ18O is controlled by air parcel trajectory and amount of rainout between source and cave site. P/Ca and U/Ca records from this stalagmite provide information on past rainfall conditions. Correlation analysis of δ18O, P/Ca and U/Ca indicates that rainfall amount was not the dominant control on δ18O composition at this cave site. Examination of a stalagmite that has diagenetically altered from aragonite to calcite shows that the δ18O system is extremely susceptible to diagenesis. Sr/Ca and U/Ca of the primary aragonite are retained in secondary calcite. Higher Mg/Ca ratios in secondary calcite compared to primary aragonite indicates that diagenetic fluid adds material to the primary carbonate. The variation in U-Th ages are caused by differential addition and losses of U and Th isotopes.
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Swabey, Stephen E. J. "Rates of natural climate change : a study of speleothems." Thesis, Open University, 1996. http://oro.open.ac.uk/54553/.
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Speleothems (cave calcite) provide many different proxy indicators for palaeoclimatic changes during the Quaternary era. Generally, the occurrence of growing speleothems is a strong proxy for global palaeoclimate, both geographically and through time. A database of speleothem U-Th ages shows some evidence for an early transition from the penultimate glacial to the last interglacial at -140 Ka BP. The database suggests an age of 63 Ka BP for the maximum cold period within isotope stage 4. Isotope stage 3 contains three periods of increased number of growing speleothems, at 40,50 and 56 Ka BP mainly in low latitude caves. The start of growth, growth rate, oxygen isotopes, carbon isotopes and luminescence intensity in two speleothems from southern Ireland provide high-resolution records of rapid palaeoclimate changes in that region during the Late Glacial. Several of these palaeoclimate proxies appear to be linked. The Younger Dryas (YO) cold event is dated at between 12.5 and 11.4 Ka BP in both speleothem records. The dominant agent of palaeoclimatic variation during the YD is probably changes in North Atlantic ocean circulation. A Microsoft Excel spreadsheet is developed as a means of rapidly converting between 14C and calendar years and vice versa.
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Lean, Candida Mary Bevan. "Geomagnetic palaeosecular variation recorded in North and Central American speleothems." Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240751.
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Nordhoff, Peter. "Stable isotope investigations on speleothems from different cave systems in Germany." Doctoral thesis, [S.l.] : [s.n.], 2005. http://webdoc.sub.gwdg.de/diss/2005/nordhoff.
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Lyons, Ruth Gladwyn Amy. "Contributions to electron spin resonance dating, with special reference to speleothems." Thesis, University of Auckland, 1990. http://wwwlib.umi.com/dissertations/fullcit/9120206.
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Electron Spin Resonance (ESR) dating has many potential applications in the fields of archaeology and Quaternary geomorphology. In particular, it offers a useful addition to more established techniques for dating speleothems, which not only have relevance to Quaternary geomorphology but may also carry palaeomagnetic and palaeoclimatic data. This work consolidates the method of ESR dating, with special reference to calcite speleothems, and contributes to several important aspects of the methodology. Using a low energy nuclear accelerator as a source of alpha particles of various energies, it is shown that the effectiveness of alpha radiation in producing paramagnetic defects is energy dependent, and approximately linearly related to the range of the incident alpha; the implications for dose rate calculations are discussed, and ranges are calculated for alpha particles of different energies for various dating materials for use in applying the above finding. The alpha/gamma effectiveness ratio, k, is experimentally determined for 18 calcite speleothems as k$/sb[/rm av]$ = 0.052 $/pm$ 0.006, which is significantly less than most previous estimates. The k-value for a coral sample is 0.055. By examining the Th-230/Po-210 ratios of 19 speleothem samples it is shown that for almost all speleothems, radon is retained within the sample until its decay; thus the full radionuclide decay chains should be used in dose rate calculations. Analysis of 'typical' calcite spectra confirms that interference between peaks of different origins and stability affects the estimate of accumulated dose (AD), and provides a rational basis for decisions on different sample preparation methods and analytical procedures. The effect of these on age estimates is examined and routine experimental methods recommended. The effect of different ESR spectrometer operating parameters is also evaluated and it is shown that the use of high microwave power avoids potentially serious underestimation of the accumulated dose (AD). A straight-forward statistical method is developed; this enables confidence limits to be derived for AD and provides a test for equivalence of AD estimates, using standard linear hypothesis techniques. A robust Geiger Muller instrument sufficiently sensitive to give estimates of relative gamma dose rates in a few minutes is developed specifically for cave dosimetry. It has the potential, with further development and cross-calibration, to become a viable method for measuring absolute environmental gamma dose rates. Serious discrepancies between two 'absolute' dosimetry methods are revealed; this and other problems of environmental gamma dosimetry are discussed. The evaluation of gamma dose rates in calcite (with respect to both laboratory and field dosimetry) and the form of the dose response curve (including the possibility of supra-linearity and non-thermal instability) are identified as areas requiring further research.
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Serefiddin, Feride Schwarcz H. P. "Paleoclimate models for western North America as inferred from speleothem isotope records /." *McMaster only, 2003.
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16
Agosta, Sarah. "Preservation and diagenesis in ancient speleothems: evidence from Bear Cave, Yukon Territory." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28844.
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Speleothems are rare in high-latitude and high-altitude caves, which is why Bear Cave in the north-western Yukon Territory is particularly unique, as it houses some of the oldest and highest latitude speleothem in the world. In this study, a detailed petrographic and geochemical study was conducted along the profile of a 68-cm long late-Miocene flowstone from Bear Cave (BC1) to reveal the processes that took place at the time of deposition, in addition to those that followed, in aims to determine its paleoclimatic suitability. These studies suggest that softer facies are generally representative of disequilibrium conditions, where in-filled textures provide evidence for diagenic phenomena; these processes ultimately obscure the original climate signal, compromising the integrity of the flowstone in terms of its paleoclimatic suitability. Conversely, harder facies are likely deposited in isotopic equilibrium and resistant to post-depositional diagenesis, and are therefore more reliable for detailed paleoclimatic analysis. The variability of the calcite sequences in the profile of BC1 imply that environmental conditions have been considerably variable of the course of deposition, reflecting alternating cool/dry (softer facies) and warm/wet (harder facies) climatic conditions. Results from radiogenic 4He-dating constrain the timeframe of deposition, with ages centering around 9.35 +/- 0.52 Ma, which are in line with regional geomorphic interpretations. This study emphasizes the importance of a complimentary petrographic study in speleothem geochemical studies used in paleoclimatic and paleoenvironmental research.
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Peckover, Maria Isabel. "Geochemical and petrographic insights from speleothems : records of Holocene Eastern Mediterranean climate." Thesis, University of East Anglia, 2017. https://ueaeprints.uea.ac.uk/69376/.
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In this thesis, new Holocene palaeoclimate information from speleothems is presented from three regions (central Peloponnese Greece, south west Turkey and the eastern forelands of the Zagros Mountains, Iran) where the spatial distribution of Holocene climate records is low. This study uses a multi-proxy approach with particular emphasis on petrography and stable isotope analysis. Holocene growth of stalagmite KTR-2 (11,900 yr BP to 6700 yr BP) from Limnon Cave in the central Peloponnese is broadly coincident with the formation of Sapropel 1. The early Holocene was generally wetter than at present. A record of the 8.2 kyr event was obtained from KTR-2 using high resolution trace element ICP-MS and micromilled stable isotope samples. Arid conditions are implied by δ18O and trace elements, with aridity probably beginning ~9000 yr BP. δ13C data suggests precipitation may have been strongly seasonal during the 8.2 kyr event. Distinct grey coloured layers in HY-8, a stalagmite from Sirtlanini Cave, SW Turkey, represent fire events occurring above the cave; there is however, no suggestion that the fires occurred during periods of relatively enhanced aridity. The palaeoclimate record spans ~5600 yr BP to the present day, but does not indicate any significant long term reduction in precipitation. The HY-8 δ18O record suggests the 4.2 kyr anomaly was a two-step aridity event occurring between 4290 and 3850 yr BP. A distinct pluvial event from 4890-4290 yr BP is also recorded by δ18O, as is evidence for the Little Ice Age (630-280 yr BP). The Holocene section of stalagmite KT-3, from the eastern forelands of the Zagros Mountains in Iran, grew from 9400 yr BP to present. The early Holocene until ~7000 yr BP was wetter than the present day. Multiple proxies show falling precipitation amounts from ~7000 yr BP, plateauing from ~3000 yr BP to present. There is very little short term fluctuation in δ18O but the overall trend has a profile similar to the decline of solar insolation in the Holocene, which appears to be responsible for the long term reduction in winter precipitation. In KT-3, the correlation between Ba/Ca and δ13C fluctuations might be a more sensitive indicator of moisture. A significant positive δ13C excursion could be recording the 8.2 kyr event. Additionally, this thesis presents a specific petrographic study from two different, but discontinuously grown, Turkish stalagmites. These stalagmites grew very differently and within different epochs. Petrography has been used to interpret and relate fabrics to their environment of formation and identified micro-dissolution as a prominent feature of growth. A link between these micro-dissolution events and stratigraphically inverted U-series dates is proposed.
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Boyd, Meighan. "Speleothems from Warm Climates : Holocene Records from the Caribbean and Mediterranean Regions." Doctoral thesis, Stockholms universitet, Institutionen för naturgeografi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-121750.
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This thesis contributes to increased knowledge on Holocene climate and environmental variability from two complex and sparsely studied areas. Using a speleothem from Gasparee Cave, Trinidad, as a paleoclimate archive, the local expression of the 8.2 ka (thousand years before 1950) climate event and associated patterns of the inter-tropical convergence zone (ITCZ) and rainfall is provided. Subsequent speleothem studies using multi-proxy analysis of stalagmites from Kapsia Cave and Alepotrypa Cave, Greece, provide records of climate, vegetation and human induced changes in the cave environment during parts of the Holocene. The speleothems from the well-studied Neolithic habitation site, Alepotrypa Cave, have produced a climate and habitation record which covers the period of 6.3-1.0 ka. The cave was inhabited between 8.0-5.2 ka and was closed by a tectonic event, which has preserved the settlement. The stable oxygen record shows the first well-dated and robust expression of the 4.2 ka dry event in the Peloponnese, places the timing of the 3.2 ka dry event within an ongoing dry period, and shows a final dry event at 1.6 ka. The North Atlantic as well as more regional drivers, such as the North Sea Caspian Pattern Index is proposed to, in a complex interplay, govern many of the climate trends and events observed. Trace element variation after the site is abandoned indicate what is interpreted as two volcanic eruptions, the Minoan eruption of Thera (Santorini) around 3.6 ka and the 2.7 ka eruption of Somma (Vesuvius). Variations in trace elements during the habitation period show clear human influence, indicating an association with specific cave activities. One of the most interesting prospects for continued work on Alepotrypa Cave is this successful marriage of speleothem studies and archeology. A framework of dates which constrain some behavior of people living in the cave is only the beginning, and there is great potential to continue finding new clues in the speleothem data.Denna avhandling bidrar till ökad kunskap om klimatets variationer och miljön i två geografiskt skilda områden på låga breddgrader och under tidsperioder inom den Holocena epoken. Genom att använda en droppsten (stalagmit) från Gasparee-grottan, Trinidad, som ett paleoklimatarkiv, har det bland annat varit möjligt att visa att Trinidad upplevde torrare förhållanden under den snabba klimatförändring som observerats ske för 8200 år sedan på många platser i världen. Denna torrare klimatsituation i Trinidad föreslås vara ett resultat av en sydlig förflyttning av den intertropiska konvergenszonen. Övriga stalagmiter som studerats för denna avhandling kommer från Kapsia-grottan och Alepotrypa-grottan som finns på Peloponnesos-halvön i Grekland. Resultaten därifrån speglar dels klimat- och vegetationsvariatoner och dels graden av mänsklig aktivitet, under tiden för ca 8000 år sedan till för 1000 år sedan. Alepotrypa-grottan är känd för att vara en av de större Neolitiska boplatserna i Grekland. Isotop- och spårämnesanalyser av stalagmiterna har bidragit med ny kunskap om tidpunkten för mänsklig aktivitet, hur människorna påverkade grott-miljön samt hur klimatet varierat efter det att grottan, genom en tektonisk händelse, stängdes för människans inverkan. Snabba klimatförändringar, för 4200 och 3200 år sedan, observerade i andra regioner, rekonstrueras här för första gången på Peloponnesos. En snabb förändring mot torrare förhållanden observeras även för 1600 år sedan. De klimatstyrande processerna föreslås vara en kombination av storskaliga processer som den nordatlantiska oscillationen och mer regionala processer som det så kallade North Sea Caspian Pattern Index. Variationer i spårämnen i stalagmiterna efter att Alepotrypa-grottan stängdes kan kopplas till två vulkaniska utbrott, nämligen det Minoiska utbrottet av Thera på ön Santorini kring 3600 år sedan och utbrottet av Somma (Vesuvius) kring 2700 år sedan. Spårämnesvariationer under bo-perioden ger tydliga indikationer på människans påverkan på grottmiljön och som delvis kan länkas till specifika aktiviteter, som eldning av dynga i grottan. Avhandlingen är ett resultat av en framgångsrik kombination av klimatstudier och arkeologisk kunskap och utgör ett viktigt underlag för fördjupat interdisciplinärt forskningssamarbete i Alepotrypa-grottan.
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript. Paper 6: Manuscript.
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Wickens, Leretta. "Geochemistry and petrography of speleothems from Turkey and Iran : palaeoclimate and diagenesis." Thesis, University of East Anglia, 2013. https://ueaeprints.uea.ac.uk/47931/.
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Speleothems contain key archives of palaeoclimatic information, which can be interpreted through multiple geochemical and petrographic proxies, and precisely dated by Uranium Series dating. As U/Th dating is only viable for samples up to approximately 700 kyr of age, U/Pb dating must be used to date older samples. In this study, U/Pb methods were used to date an aragonite layer in a speleothem from Iran, following the use of autoradiography to select samples with appropriately high uranium. Aragonite is metastable at earth surface conditions, and is therefore prone to recrystallisation as calcite if it comes into contact with a fluid that is undersaturated with respect to aragonite. This process affected two speleothems from Dim Cave, SW Turkey, and one speleothem from Torang Cave, Iran. The older Dim Cave stalagmite, which precipitated during MIS 5e, was not identified as a recrystallised stalagmite at first, as the mineralogy of the growth axis appeared to show a change in primary mineral rather than recrystallisation. Despite the fact that recrystallisation had occurred, it was possible to create an age model, as the system had not opened to a great degree. The persistence of an aragonite layer in this speleothem, as well as several other geochemical proxies, indicates that an arid phase occurred during early MIS 5e in SW Turkey. The second recrystallised speleothem from Dim Cave provides useful insights into the geochemical and petrographic character of recrystallised speleothems. The recrystallised speleothem from Torang Cave produced a record of climatic instability in southern Iran during MIS period 9- 7, although the age model was not precise enough to draw precise conclusions. A small aragonitic Holocene growth from Dim Cave grew during a time which corresponds to an early Holocene pluvial period that affected the entire eastern Mediterranean Basin, coinciding with the deposition of Sapropel 1.
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Biller, Nicole Brooke. "Widespread permafrost thaw during Marine Isotope Stages 11 and 13 recorded by speleothems." Thesis, Boston College, 2017. http://hdl.handle.net/2345/bc-ir:107655.
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Thesis advisor: Jeremy D. ShakunArctic permafrost contains a substantial stock of carbon that could be released to the atmosphere as CH4 and CO2 upon thawing, making it a potentially powerful amplifier of future warming. The sensitivity of permafrost to climate change is uncertain, however, and occurs on time scales longer than those captured by the instrumental record. Speleothems – cave precipitates deposited from flowing or dripping water – in currently frozen regions record past episodes of thaw, which can be used to assess the response of permafrost to long-term warmth. Here, we present 90 uranium-thorium ages on speleothems from across the North American Arctic, sub-Arctic and northern alpine regions to reconstruct a 600-kyr permafrost history. Widespread speleothem growth supports an episode of extensive permafrost thaw during the Marine Isotope Stage 11 interglacial about 400 ka, when global temperature was only slightly warmer than pre-industrial conditions. Additional growth is evident during MIS 13, curiously, a smaller magnitude interglacial. Ice-core records of atmospheric greenhouse gases do not show elevated concentrations at these times, perhaps suggesting that the permafrost carbon pool was smaller than today or released gradually enough to be buffered by other reservoirs
Thesis (MS) — Boston College, 2017
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Earth and Environmental Sciences
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Xia, Qikai. "High precision TIMS U-Th disequilibrium dating and C, O, Sr isotope-based multi-proxy palaeoclimatic study of Speleothems in Australia /." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18421.pdf.
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Lepley, Scott William. "A high-resolution record of Holocene El Niño cyclicity from Crevice Cave, Missouri /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1420934.
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Soto, Limaris R. "Reconstruction of late holocene precipitation for Central Florida as derived from isotopes in speleothems." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001330.
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Richards, David Alan. "Pleistocene sea levels and palaeoclimate of the Bahamas based on ²³⁰Th ages of speleothems." Thesis, University of Bristol, 1995. http://hdl.handle.net/1983/94beb916-63ef-4f43-a04b-442666097839.
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Steponaitis, Elena Anne. "Deep-lake carbonates and speleothems as high-resolution archives of paleohydrology in the Bonneville Basin, UT." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103248.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references.
Precisely dated terrestrial paleoclimate records are indispensable for understanding how different regions respond to global-scale climate variability. Here, we focus on developing precisely dated records from the Bonneville Basin, a large basin in the eastern U.S. Great Basin. This region is known to have been highly sensitive to hydroclimate changes during the past glacial period; closed-basin lakes in this region have been studied for over a century. We present lake and speleothem records from the Bonneville Basin that are anchored by high-precision U-Th ages. Deep-lake carbonates are deposits that form beneath the surface of lakes in crevices and protected spaces. We explore these deposits as an archive of past hydrological change in the Bonneville Basin. Deep-lake carbonates deposits were collected from varying elevations in the basin and microsampled for U-Th dating. The results of this work improve constraints on existing lake level information for Lake Bonneville. Additionally, we present [delta]234U data from these carbonates that records changes in weathering, and by extension, hydrology, in the Bonneville Basin. 87Sr/86Sr ratios of deep-lake carbonates reflect relative changes in fluvial input between the northern and southern sub-basins of the Bonneville Basin, allowing for the reconstruction of past precipitation patterns. This record shows that there were distinctly different patterns of atmospheric circulation over the Bonneville Basin during Heinrich Event 2 and the Last Glacial Maximum. Finally, we present records Mg/Ca ratios and [delta]13C values of speleothems from Lehman Caves, NV, located on the western edge of the Bonneville Basin. These records suggest that the onset of mid- Holocene drying in the Great Basin was at 8.2 ka, coincident with the collapse of the Laurentide Ice Sheet.
by Elena Anne Steponaitis.
Ph. D.
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Truebe, Sarah, and Sarah Truebe. "Past Climate, Modern Caves, and Future Resource Management in Speleothem Paleoclimatology." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621105.
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My research focuses on reconstructing past climate in southern Arizona using cave deposits called speleothems. However, this necessitates a broader perspective than simply a geochemical time series, and therefore, I also investigate modern cave systems using a combination of modeling and observational datasets. Finally, cave deposits are fundamentally non-renewable resources, and sampling for past climate reconstruction can be destructive, unlike other cave uses. My last investigation is focused on developing possible best practice recommendations for paleoclimate scientists and other cave stakeholders moving forward. We developed two new stalagmite records of past climate variability in southern Arizona over the past 7000 years. Past climate reconstruction from two caves (Cave of the Bells and Fort Huachuca Cave) highlights insolation control of southern Arizona hydroclimate from 7000-2000 years before present. Additionally, comparison between two stalagmites with different seasonal sensitivities uncovers a few eras of multi-decade long droughts in southern Arizona, which align with other regional reconstructions of past climates and elucidate forcings on Southwest paleoclimate as emergent from both external (insolation) and internal climate variability in the Pacific and Atlantic Ocean basins. Although the oxygen isotopic signal of cave calcite in speleothems is complex, agreement with these other records indicates that the speleothem records from these caves primarily record a climate signal.Modeling and monitoring of modern caves both helps us interpret paleoclimate records and enhances our understanding of cave systems in their own right. Modeling of Cave of the Bells dripwaters demonstrates the effect of storage and mixing on the dripwater oxygen isotope signal; non-climate processes can imprint on dripwater variability on multidecadal timescales. Monitoring shows that on very small spatial scales, every cave is different, and even sites within the same cave respond uniquely to surface climate. Most notably, calcite oxygen isotopic composition, used to reconstruct past climate, shows seasonal variability unrelated to dripwater and surface rainfall oxygen isotope variability. Substantial oxygen isotope disequilibrium is identified at numerous caves sites in southern Arizona, and this understanding aligns with a growing number of cave studies that demonstrate the long-held assumption of isotopic equilibrium in cave systems may not always be valid or that the way in which we define isotopic equilibrium insufficiently captures the variety of processes controlling the oxygen isotopic composition of speleothems. Overall, however, monitoring can identify stalagmites that are more sensitive to surface climate and less sensitive to these in-cave processes by identifying sites with dripwater variability responses to surface rainfall variability and sites that precipitate close to oxygen isotopic equilibrium. Finally, a major missing component in speleothem research is the fact that speleothems take thousands and sometimes hundreds of thousands of years to form. They are non-renewable resources on human timescales, and habitat for myriad microbes that have yet to be identified. Removal of speleothems for paleoclimate research is one of the only destructive uses of these deposits. With that in mind, I also analyze current methods of collecting speleothems and develop a framework based on two surveys of scientists and stakeholders to assist scientists and managers when evaluating potential methods of incorporating cave conservation into the speleothem sampling process. Thus, I approach caves from a variety of angles and timescales, from the past through the present to the future, illuminating caves as complex scientific and social systems.
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Vaks, Anton. "Quaternary paleoclimate of north-eastern boundary of the Saharan Desert reconstruction from speleothems of Negev Desert, Israel /." Jerusalem : Geological Survey of Israel, 2008. http://www.gsi.gov.il/Eng/_Uploads/252GSI-14-2008.pdf.
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Thesis (Ph.D.)-- Hebrew University, 2008.Title from PDF t.p. (viewed on March 2010). At head of title : Ministry of national infrastructures, Geologocal survey of Israel. "This work was submitted for the degree "Doctor of Philosophy" to the Senate of the Hebrew University, Jerusalem."/T.P.
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Hasegawa, Wataru. "Relationships among Cave Micrometeorology, Speleothem Growth and Surface Environment Revealed by Cave Monitoring Studies." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199113.
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Pejoski, Dejan <1994>. "Palaeoenvironmental changes revealed through multielemental proxies in speleothems – Insights and perspectives from Cave KNI-51 in Kimberly, Australia." Master's Degree Thesis, Università Ca' Foscari Venezia, 2021. http://hdl.handle.net/10579/18913.
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Climate change manifests as a complex synergy of biogeochemical and physical variations taking place within all earth compartments at different spatial and temporal scales. Paleoclimatic archives spread around the globe capture some of those variations and preserve their signal in the form of specifically representative biotic and physicochemical parameters (proxies). Karsts deposits known as speleothems are important geological and geochemical climate archives, mostly studied for changes in their stable-isotope composition (δ18O and δ13C) to reconstruct past variations in vegetation, temperature or rainfall regimes. Trace elements have been also reported as potential proxies of annual and multi-annual climatic variations in speleothems, and have been shown as particularly effective in recording extreme phenomenon such as droughts and floods. Still, the intricacy of elemental fractionation processes during transport, deposition, crystallization and the complex and site-specific forcing of environmental settings make the interpretation of trace elements pattern in speleothems extremely challenging. The goal of the thesis is: i) to provide a comprehensive and critical review of elemental levels and ratios as paleoclimate proxies in speleothems; ii) investigating the applicative potential of elemental proxies for paleclimate reconstruction through the analysis of a stalagmite recently collected at Cave KNI-51 located in the Ningbing Range of the eastern Kimberley region of Western Australia; iii) to provide a critical perspective for future in-depth studies on the same cave.
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Miller, Brett Alan. "δ13C of Cave Speleothems Located in Kentucky and Ohio, U.S.A.: Implication for Paleovegetation and Paleoclimate Studies." Bowling Green State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1205450304.
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Novello, Valdir Felipe. "Reconstituição paleoclimática do holoceno recente com base em estalagmites da região central do Estado da Bahia." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/44/44142/tde-11052015-153510/.
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A partir de registros de \'delta ANTPOT.18 O\' e \'ANTPOT.13 C\' e das taxas de crescimento de espeleotemas precisamente datados pelo método U-Th foi possível reconstituir a paleopluviosidade dos últimos 3 mil anos da região central do estado da Bahia. Os registros de alta resolução (\'DA ORDEM DE\' 4 anos) propiciaram caracterizar a influência dos padrões atmosféricos e da temperatura da superfície do mar (TSM) observados atualmente nos oceanos Atlântico e Pacífico na paleoprecipitação da região. Através da comparação direta entre os dados de \'delta ANTPOT. 18 O\' da estalagmite TR5 (com resolução amostral de 6 meses) com estações de monitoramento pluviométrico da região, foi possível relacionar as variações do \'delta ANTPOT. 18 O\' do espeleotema com a variação da pluviosidade mostrando que, valores mais negativos no registro isotópico são representativos de maior precipitação e vice-versa. Essa relação está de acordo com o fator \"amount effect\", que atua na variação das razões isotópicas do oxigênio da chuva na região tal como foi identificado em estudos da série histórica de monitoramento das estações IAEA-GNIP e por simulações computacionais que mostram a variação dos valores de \'delta ANTPOT. 18 O\' na atmosfera. O registro paleoclimático mostrou que uma progressiva aridificação vem ocorrendo na região central da Bahia nos últimos 3 mil anos, acompanhando o aumento da insolação de verão. Nesse intervalo de tempo, foram encontradas sequências de eventos úmidos abruptos que ocorrem periodicamente em escala centenial. Entre esses eventos, destaca-se o que ocorreu entre \'DA ORDEM DE\' 822-642 A.C. que é coincidente com intervalo de extremo frio na Europa e com o período de mínimo solar detectado na variação da irradiância. Já, durante a Anomalia Climática Medieval (ACM) e a Pequena Era do Gelo (PEG) o registro mostrou condições secas próximas a detectadas atualmente. Através de análises estatísticas realizadas nas séries temporais obtidas a partir do registro paleoclimático das estalagmites, foi detectado uma periodicidade de \'DA ORDEM DE\' 65 anos correlata com a Oscilação Multidecenal do Atlântico (OMA) em todo o registro da parte central da Bahia. Influências decorrentes da TSM do oceano Pacífico mostraram-se presentes durante eventos abruptos e períodos anômalos úmidos e secos.We present the first high resolution (\'DA ORDEM DE\' 4 years) precipitation record from central portion of Bahia state, covering the last \'DA ORDEM DE\' 3000 yrs from \'ANTPOT. 230 Th-dated\' stalagmites oxygen isotope records. Our record shows abrupt fluctuations in rainfall tied to variations in the intensity of the South American summer monsoon (SASM), including the periods corresponding to the Little Ice Age (LIA), the Medieval Climate Anomaly (MCA) and a period around 2800 yr B.P. Unlike other monsoon records in southern South America, dry conditions prevailed during the LIA in the Nordeste. Spectral, wavelet and cross-wavelet analyses of our record detected several periodicities from multidecadal to centennial time scales, particularly centered on 65 and 210 years, which have been linked to Atlantic sea surface temperature (SST) variations and solar variability, respectively. Here we show that changes in SASM activity in the region are mainly associated with variations of the Atlantic Multidecadal Oscillation (AMO) and to a lesser degree caused by fluctuations in tropical Pacific SST. Comparisons between TR5 \'delta ANTPOT. 18 O\' stalagmite record (\'DA ORDEM DE\' 6 mouths resolution) with local meteorological station showed that variations in \'delta ANTPOT. 18 O\' speleothem composition are in agreement with variations in the amount of rainfall over central Bahia. The same correlation was also identified in computing simulations based on IAEA-GNIP monitoring stations data. The \'delta ANTPOT. 18 O\' speleothem record shows a clearly trend toward dry conditions in central Bahia since the last 3 thousand years in agreement with solar insolation curve. In addition, the \'delta ANTPOT. 18 O\' record od DV2 sample shows several sequence of wet event at centennial time-scale. Among these events we call attention to the event occurred at \' DA ORDEM DE\' 822-642 D.C., coincident with an abrupt cold event recorded in Europe and with a minimum of solar irradiance. In other hand during the MCA and the LIA the record shows dry conditions, close to current values.
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Ritter, Simon Michael [Verfasser], and Margot [Akademischer Betreuer] Isenbeck-Schröter. "Unravelling the formation of Hells Bells: underwater speleothems from the Yucatán Peninsula in Mexico / Simon Michael Ritter ; Betreuer: Margot Isenbeck-Schröter." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://d-nb.info/1204481121/34.
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Mischel, Simon André [Verfasser]. "Multi-proxy reconstruction of Holocene and Late Glacial climate variability using precisely dated speleothems from the Herbstlabyrinth, central Germany / Simon André Mischel." Mainz : Universitätsbibliothek Mainz, 2016. http://d-nb.info/1119102847/34.
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Genuzio, Giulia <1990>. "Reconstructing fire history from 1700 to present through the analysis of organic compounds in speleothems: a high resolution study from north-western Australia." Master's Degree Thesis, Università Ca' Foscari Venezia, 2021. http://hdl.handle.net/10579/18993.
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Organic molecules are excellent indicators of past fires. This research work analyzes the polycyclic aromatic compounds present in stalagmite to assess whether they are related to combustion processes and therefore suitable for the reconstruction of paleo fires in northwest Australia. The further analysis of n-alkanes provides information on the type of vegetation present above the cave as these molecules are proxies of vegetation cover. The work requires the preparation of samples by drilling, acid digestion, liquid-liquid extraction and concentration in organic clean room. This is followed by gas chromatographic analysis combined with single and triple quadrupole mass spectrometry. The expected results will enable to evaluate past fires in terms of intensity, frequency and type of vegetation affected.
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Ruiz, Verónica Marcela Ramirez. "Reconstituição Paleoclimática dos últimos 5.500 anos nos Andes Orientais da Colômbia." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/44/44142/tde-03122014-093609/.
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Registros geocronológicos e isotópicos de\'\'delta\' POT.18 O\' e \"delta\'POT.13 C\' obtidos em alta resolução em estalagmites da caverna Caracos, município colombiano El Peñon, permitiram reconstituir a paleopluviosidade dos últimos 5500 anos nos Andes Orientais da Colômbia. Esses registros permitiram discutir as variações climáticas ocorridas em escala decadal durante o Holoceno Médio e Inferior e caracterizar a influência dos padrões atmosféricos e da temperatura da superfície do mar nos oceanos Atlântico e Pacífico. O estudo paleoclimático realizado na Colômbia foi apoiado na calibração prévia realizada na caverna Caracos que indicou uma correlação positiva entre a assinatura isotópica da água da chuva e do gotejamento das estalagmites CAR1, CAR2 e CAR3, como também, que a deposição isotópica destas ocorreu em equilíbrio. A partir dessa observação, foi interpretado que a variação dos valores de \'\'delta\'POT.18\' O dos espeleotemas da caverna Caracos ocorreu em função do condicionante isotópico amount effect (efeito quantidade) e da fonte de umidade. O registro isotópico de El Peñon mostrou que a variação da chuva, entre 3500-2500 anos BP e durante o Anomalia Climática Medieval e a Pequena Idade do Gelo, nos Andes Orientais da Colômbia esteve relacionada com as Oscilações do Atlântico e Pacífico, como também ao posicionamento meridional da Zona de Convergência Intertropical. Tais mudanças na paleoprecipitação, além de serem observadas na Colômbia, também estão registradas em outros locais como em Cariaco, na Venezuela, em Pumacocha e no México. Além disso, observou-se através de análises estatísticas das séries temporais dos registrosisotópicos de El Peñon, que as mudanças da paleopluviosidade observadas na Colômbia nos últimos 1500 ocorreram com uma peridiodicidade de ~ 65, 30 e 5 anos, relacionadas respectivamente com a Oscilação Multidecenal do Atlântico (OMA), com a Oscilação Decadal do Pacífico (ODP) e com os eventos El Niño Southern Oscilation. Os ciclos que mostram as análises estatísticas tem variações ao longo do registro, mostrando enfraquecimento/ fortalecimento em períodos como a ACM, LIA e CWP. Essa relação está de acordo com o fator \"amount effect\", que atua na variação das razões isotópicas do oxigênio da chuva na região tal como foi identificado em estudos da série histórica de monitoramento das estações IAEA-GNIP, mostrando que nas áreas tropicais é o principal componente no fracionamento isotópico de oxigênio.From records of \'\'delta\'POT.18\' O and 13C and growth rates of speleothems precisely dated by U-Th method was possible to reconstruct the paleo rainfall the last 5500 years in the region of the Eastern Andes in Colombia. Records high-resolution (~ 1 year for the past 1500 years) propitiated characterize the influence of weather patterns and sea surface temperature (SST) currently observed in the Atlantic and Pacific oceans in the region paleo rainfall. Through the rainfall data collected in the study area for a year, a comparison of rainfall data of Bogota and the d18O record of stalagmites CAR1, CAR2 and CAR3, was possible to relate the variations of \'\'delta\'POT.18\' O of speleothems with variation in rainfall; this showed that more negative isotopic values in the registry are representative of greater precipitation and vice versa, in addition to a component of variation due to moisture source. This relationship is consistent with the factor \"amount effect\", which acts on the variation of the oxygen isotope ratios of rain in the region as was identified in studies of the historical series of monitoring stations IAEA-GNIP, showing that in tropical areas is major component in the oxygen isotopic fractionation. The isotope record of El Penon showed a relationship with the variations in the Atlantic and Pacific oscillations, as observed in other records of South America. Were also recorded changes in the location of the ITCZ that influences rainfall in the area, as are the periods between 3500-2500 years BP, ACM and LIA, changes are also recorded in other places like Cariacos, Pumacocha and Mexico. Through statistical analyzes in the time series obtained from the paleoclimate record of stalagmites of the last 1500 years, periodicity of ~ 65 years was correlated with the detected Multidecenal Atlantic Oscillation (OMA) in the entire record of El Penon, and periodicities between ~ 30 years associated with the Pacific Decadal Oscillation (PDO) and between ~ 5 with respect to ENSO events. The cycles show statistical analyzes have variations throughout the record, showing weakening / strengthening in periods such as ACM, LIA and CWP.
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Strikis, Nicolas Misailidis. "Atividade do Sistema de Monção Sul-americana na porção central do Brasil durante o último período glacial a partir da aplicação de isótopos de oxigênio em espeleotemas." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/44/44142/tde-27082015-095244/.
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Estudos paleoclimáticos com base em registros isotópicos em espeleotemas apontam para um forte controle da insolação e das variações da circulação oceânica sob o transporte de umidade pela Zona de Convergência do Atlântico Sul, com grande impacto sobre a distribuição de chuvas na região do Brasil central. No entanto, pouco se sabe sobre as mudanças paleoclimáticas em áreas diretamente afetadas pela Zona de Convergência do Atlântico Sul (ZCAS). De fato, reconstituições paleoclimáticas de alta resolução na América do Sul, relacionadas a variações do regime hidrológico limitam-se a regiões localizadas na borda do Sistema de Monções Sul-americano (SMSA), próximos às zonas costeiras e junto às regiões dos Altiplanos bolivianos e Amazônia peruana. Esta tese apresenta uma contribuição ao estudo paleoclimático do Sistema de monção Sul-americana a partir da reconstituição da paleoprecipitação do Brasil central com base em registros isotópicos de \'\'delta\' POT.18\'O em estalagmites da região norte de Minas Gerais, precisamente datas pelo método U-Th. As estalagmites analisadas foram coletadas nas cavernas Lapa Grande, Lapa dos Anjos e Lapa Sem Fim. A reconstituição paleoclimática abrange a maior parte dos últimos 85 mil anos. Além disso, foram realizados estudos de monitoramento geoquímico-isotópico nas cavernas Lapa Sem Fim e Lapa dos Anjos com objetivo de aumentar a confiabilidade das interpretações paleoclimáticas e paleoambientais dos registros isotópicos de espeleotemas. O monitoramento isotópico envolveu a análise comparativa dos valores de \'\'delta\' POT.18\'O\'\' da água da chuva com o das soluções de gotejamento de estalactites e de amostras de carbonato depositada em vidros de relógio posicionado abaixo dos gotejamentos. Avaliações sistemáticas do fator de fracionamento isotópico realizadas com bases nos dados de \'\'delta\' POt.18\'O dos gotejamentos e do carbonato precipitado indicam que a composição isotópica \'\'delta\' POT.18\'O da calcita depositada em estalagmites é, em parte, controlada por efeitos de fracionamento cinéticos. As variações do fator de fracionamento tem relação com alterações das taxas de degaseificação, por sua vez, controladas por oscilações da concentração de CO 2 da atmosfera da caverna. Apesar das variações observadas no fator de fracionamento isotópico, variações sazonais e interanuais do \'\'delta\' POT.18\'O dos gotejamentos encontram boa correspondência com o \'\'delta\' POT.18\'O medido nos carbonatos dos vidros de relógio. Na escala de tempo orbital, as flutuações climáticas registradas no centro-leste do Brasil apresentam um acoplamento parcial com a forçante de insolação. Ao longo dos últimos 85 mil anos, a relação entre a paleoprecipitação registrada a partir dos dados de \'\'delta\' POT.18\'O de espeleotemas da área de estudo e a curva de insolação é restrita ao intervalo entre 60 e 85 mil anos AP. A fraca relação entre a paleoprecipitação e a forçante de insolação registrado na região centro-leste do Brasil é discutida no contexto de uma provável influência das condições de contorno do clima no período glacial e a relação com a intensidade e posição da ZCAS. Na escala de tempo milenar, foi analisada a variabilidade do sistema de monções na porção leste da ZCAS e a sua relação com oscilações climáticas de escala milenar registradas nas regiões de altas latitudes do Hemisfério Norte durante o último período glacial. Particularmente, durante o Estagio Marinho Isotópico 3 variações na intensidade das monções na região da ZCAS mimetizam as oscilações abruptas de temperatura determinadas pelas transições entre os eventos estadiais (frios) e interestadiais (quentes) registrados na estratigrafia isotópica de \'\'delta\' POT.18\'O dos testemunhos de gelo da Groenlândia. Por fim, foram discutidos eventos abruptos e de curta duração de aumento de chuvas identificados nos dados de alta resolução de \'\'delta\' POT.18\'O da estalagmite ao longo do último milênio. Os quais apresentaram boa relação com eventos de maior deposição de sulfetos de aerossóis vulcanogênicos registrados em testemunhos de gelo do Hemisfério Norte. Os resultados indicam uma alta suscetibilidade das chuvas de monções do Brasil central à ocorrência de erupções vulcânicas de grande magnitude. Estes eventos úmidos teriam sido impulsionados pelo deslocamento para sul da Zona de Convergência Intertropical, em resposta ao esfriamento da temperatura da superfície do mar do Atlântico norte, o que aumenta convergência de umidade na região sob o domínio do sistema de monção Sul-americano.Paleoclimatic studies based on speleothem isotope records suggest that variation in insolation and ocean circulation plays an important role in controlling the moisture transport along the South Atlantic Convergence Zone (SACZ), causing important impacts for rainfall distribution over central Brazil. However, little is known about paleoclimate changes in regions directly affected by the SACZ close to its modern axis. Indeed, on South America, high resolution paleoclimate reconstructions related to changes in the hydrologic regime are concentrated in the border of monsoon system, near the coastal areas, in the Bolivian Altiplano and in the Peruvian Amazon Forest. This thesis presents a paleo-precipitation reconstruction for central-eastern Brazil using \'\'delta\' POT.18\'O time series from speleothems precisely dated by U-Th method. The speleothems used in this study were collected in three distinct caves located in northern Minas Gerais state: Lapa Sem Fim, Lapa dos Anjos and Lapa Grande. The paleo-precipitation reconstruction presented here covers most of the last 85 kyr. In addition isotopic monitoring program were performed at Lapa Sem Fim and Lapa dos Anjos cave sites in order to provide a better understanding of the paleoclimatic and paleoenvironmental information recorded in the speleothem stable isotope time series. The isotopic monitoring comprised the comparative analysis of \'\'delta\' POT.18\' O from rain water with those from cave dripwaters and also from samples of modern carbonate precipitated in watch glasses underneath dripping sites. Systematic evaluation of the isotopic fractionation factor based on \'\'delta\' POT.18\'O from the dripping water solution and from the carbonate recently deposited suggests that the \'\'delta\' POT.18\'O of calcite deposited in the stalagmites is, in part, controlled by kinetics isotopic effects. The fluctuations of the fractionation factors are related to seasonal changes in the degassing rate that are controlled by the oscillations in the atmospheric CO2 concentration of the monitored caves. Despite of the variations of the isotopic fractionation factor, seasonal and interannual variations of \'\'delta\' POT.18\'O recorded from drippings present good correspondence with \'\'delta\' POT.18\'O recorded in the carbonate from watch glasses. During the last 85 kyr BP monsoon precipitation reconstructed from the \'\'delta\' POT.18\'O speleothem records from central-eastern Brazil show a mismatch with the insolation precession curve, except for the interval between 60 and 85 kyr BP. The limited coupling observed between orbital forcing and monsoon precipitation over central-eastern Brazil is attributed to an additional forcing by the glacial boundary conditions that significantly influence the position and strength of the SACZ. It also was investigated the precipitation variability on the millennial time-scales during the last glacial period over the eastern portion of the South Atlantic Convergence Zone region. The present results indicated a strong association with climate events recorded at high latitude areas of North Hemisphere. Particularly during the Marine Isotope Stage 3, variations in the intensity of SACZ mimics abrupt oscillations pacing by the transitions of stadial (cold) and interstadial (warm) events recorded in the oxygen isotope stratigraphy of Greenland ice cores. During the last millennium, abrupt events of increase in monsoon precipitation recorded in the high resolution \'\'delta\' POT.18\'O record from Anjos1 stalagmite appear to be in good agreement with episodes of large volcanic eruptions and sulfate emissions occurred in the Northern Hemisphere. Indeed, the \'\'delta\' POT.18\'O results indicate a strong sensitivity of the South American monsoon system to large volcanic eruptions, because of radiative cooling of the Northern Hemisphere. As a result the Intertropical Convergence Zone is displaced southward, enhancing moisture influx into the South American monsoon domain.
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Budsky, Alexander [Verfasser], and Denis [Akademischer Betreuer] Scholz. "Palaeoclimate reconstruction of the last 200 ka in south-eastern Spain, based on proxies of speleothems from Cueva Victoria / Alexander Budsky ; Betreuer: Denis Scholz." Mainz : Universitätsbibliothek der Johannes Gutenberg-Universität Mainz, 2020. http://d-nb.info/1227119054/34.
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Boop, Liana Marie. "Characterization of the Depositional Environment of Phreatic Overgrowths on Speleothems in the Littoral Caves of Mallorca (Spain): a Physical, Geochemical, and Stable Isotopic Study." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5187.
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Phreatic overgrowths on speleothems (POS) are one of many sea-level proxies available to Quaternary geologists in Mallorca; these carbonate encrustations form at the air-water interface in cave passages flooded with brackish water. POS are ideal for reconstruction of western Mediterranean sea level because they are widespread in Mallorca's caves, can be precisely dated by U-series methods, constrain sea-level stands to sub-meter elevation, and are well preserved and accessible in the subterranean environment.
This research investigates the POS depositional environment, which is relatively understudied compared to the other proxies used for sea-level reconstructions. This disparity has led to assumptions on many aspects of the POS precipitation. Further, POS are typically composed of calcite, but sometimes the metastable polymorph aragonite is present instead. Two caves were studied because of the presence of a modern POS horizon of aragonite and calcite: Cova des Pas de Vallgornera (Vallgornera) and Coves del Drac (Drac), respectively.
High-resolution air and water physical parameters were collected for the first time, along with monthly water samples for stable isotope and elemental analysis. This 16-month record was supplemented with detailed geochemical studies throughout the project, including water-column profiles and CO2 sampling campaigns.
The water level in both caves preserves the semi-diurnal Mediterranean Sea tide signal, with a lag of approximately four hours. The fluctuation in both caves is slightly attenuated, and the direct effects of barometric pressure and precipitation could not be discerned from the primary control of tidal pumping. Calculations based on salinity and isotope analysis show that less than 20% of the solution in each cave is seawater.
Degassing of CO2 from the cave water to air was documented at both locations, with sporadic calcium carbonate supersaturation. These conditions are strongly dependent on annual cave ventilation, which becomes active during winter when cold, dense tropospheric air sinks into the subsurface. In addition to seasonal thermo-circulation, fluctuating water level displaces cave air and likely initiates tropospheric exchange throughout the year. This process primarily occurs through fissures in thin overlying bedrock at Vallgornera and through the large entrance in Drac.
Higher elemental ratios (Mg:Ca, Sr:Ca, Mg:Sr) known to enhance aragonite precipitation or inhibit calcite precipitation were recorded in Vallgornera's water. A linear correlation with salinity was not observed, so higher ratios in Vallgornera must be contributed from differences in lithology, bedrock weathering intensity, or nearby rising thermal waters.
In summary, this research confirms POS strengths as sea-level proxies from geochemical and hydrological perspectives. These carbonate encrustations are precipitated at the air-water interface, which fluctuates as an attenuated expression of Mediterranean Sea tide. Degassing of CO2 from the cave water to air, which promotes calcium carbonate supersaturation, is the major control on POS deposition, and is facilitated by winter ventilation and likely water-level fluctuations. CO2 degassing (and theoretically precipitation of POS) in isotopic equilibrium is possible in caves with restricted ventilation (small/sealed entrances, small passages). Aragonite may be precipitated instead of calcite because of local modifications to the geochemical system from bedrock weathering or contributions from deep groundwater.
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Turgeon, Steven Charles. "Petrography and discontinuities, growth rates and stable isotopes of speleothems as indicators of paleoclimates from Oregon Caves National Monument, southwestern Oregon, United States of America." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ60971.pdf.
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Utida, Giselle. "Variações paleoambientais e paleoclimáticas durante o holoceno no Rio Grande do Norte a partir do estudo de registros geoquímicos de sedimentos de lagos e cavernas." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/44/44142/tde-24022016-135109/.
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A porção norte da região Nordeste do Brasil é uma das áreas mais interessantes para estudo dos mecanismos e processos relacionados à variação de pluviosidade dos trópicos, pois a maior parte da precipitação anual está associada à migração meridional da Zona de Convergência Intertropical do Atlântico (ZCIT). O clima no Nordeste sofreu alterações durante o Holoceno, no entanto, as interpretações paleoclimáticas são ainda muito controversas devido a pequena quantidade de estudos. De forma a contribuir para a discussão sobre mudanças paleoclimáticas e paleoambientais do Nordeste brasileiro, este estudo realizou análises geoquímicas, micropaleontológicas, biogeoquímica e de isótopos de deuterium e carbono em sedimentos lacustres e guano, e análises de isótopos de oxigênio e carbono em espeleotemas do Holoceno Médio e Tardio. Os estudos da Lagoa do Boqueirão sugeriram que sua formação ocorreu devido a dinâmica fluvio-eólica, que resultou em barramentos dos canais fluviais durante o período úmido do Holoceno. A transição entre o sistema fluvial e lacustre, que marca o barramento, foi definido em torno de 4.500 anos BP pela substituição de espículas de esponjas, tipicamente fluviais, pelas diatomáceas lacustres, predominantemente Mastogloia smithii var. lacustres. Foi demonstrado que a formação e as flutuações da profundidade da Lagoa do Boqueirão não estavam associadas a precipitação regional. As variações paleoclimáticas da Lagoa do Boqueirão e da Caverna do Trapiá puderam ser acessadas através dos dados de \'delta\'D em ácidos n-alcanóicos de 28 carbonos, produzidos por vegetação terrestre e macrófitas aquáticas, e dados de \'\'delta\'POT.18\'O dos espeleotemas. Valores mais positivos (negativos) desses isótopos indicaram que durante o MCA (LIA) a região apresentava condições de seca (umidade), devido ao posicionamento mais ao Norte (Sul) da ZCIT, que migrou em direção ao Hemisfério mais aquecido de acordo com a correlação observada com a Oscilação Multidecadal do Atlântico (OMA). A porção norte do NEB apresentou paleoclima diferente em relação ao da porção sul do NEB durante o LIA, que estava seco devido ao deslocamento da Zona de Convergência do Atlântico Sul (ZCAS) mais para sul, assim como a ZCIT, que não afetou a porção sul do NEB. Mudanças paleoambientais foram também definidas com base na idade de sequências sedimentares clásticas datadas por LOI e pelos depósitos de guano em condutos de cavernas em Felipe Guerra-RN. A deposição de sedimentos terrígenos na caverna Urubu entre 7 to 4 ky B.P. cave foi cronologicamente associada a clima mais úmido, o que é apoiado pelo baixos valores de \'\'delta\' POT.18\'O values de espeleotemas. Esse período também foi marcado pelo aumento da contribuição de de carbono orgânico do solo como indicado por valores mais baixos de \'\'delta\'POT.13\'C dos mesmos espeleotemas. Uma transição abrupta para clima mais seco pode está associada ao final da sedimentação clástica na caverna por volta de 4.2 ky devido a interrupção do fluxo do rio subterrâneo e completa erosão do solo ao redor da caverna. A erosão do solo é ressaltada por altos valores de \'\'delta\'POT.13\'C dos espeleotemas próximos aos da rocha encaixante (~0 %0). Estes resultados demonstraram uma relação entre preenchimento sedimentar da caverna Urubu com a formação e erosão de solo na sua volta. Esse aumento de aridez, particularmente nos últimos três mil anos na região, foi também importante para preservação de depósitos de guano sobre os sedimentos clásticos, visto que esse material é bastante solúvel. As idades das camadas de guano foram utilizadas para definir períodos de alta ocupação das cavernas por morcegos entre 1730 and 677 cal. anos A.P. e 200 cal anos A.P. até o recente. Durante o evento MCA houve redução na acumulação de guano que levou a um hiato deposicional por conta que o clima seco desfavoreceu a sobrevivência dos morcegos na região. A acumulação de guano voltou a ocorrer a 200 anos atrás, provavelmente porque a população de morcegos foi reestabelecida, devido a clima mais úmido.The northern sector of Nordeste of Brazil (NEB) is one of the most interesting regions to study mechanisms and processes related to fluctuations tropical rainfall, as the majority of annual precipitation is associated to the meridional migration of Intertropical Convergence Zone (ITCZ). Climate in NEB changed during the Holocene, although paleoclimatic interpretations are still controversial due to small number of studies. This study contribute to the discussion about paleoclimatic and paleoenvironmental changes of NEB by using geochemistry, micropaleontological, biogeochemistry and deuterium and carbon isotope analyses in lacustrine sediments and bat guano, and also speleothem isotope records from middle to late Holocene. Studies from Boqueirão Lake suggested that its formation occurred due to the fluvio-eolian dynamic, which resulted in blockage of fluvial channels during the holocenic humid period. Transition between fluvial and lacustrine system recorded the barrage formation and was defined around 4,500 years BP and suggested by the substitution of fluvial sponge spicules to lacustrine diatoms, mainly Mastogloia smithii var. lacustres, preserved in sediments. These data demonstrated that depth fluctuations of Boqueirão Lake were not associated to local precipitation accumulation. Paleoclimatic changes were reconstructed from Boqueirão Lake and Trapiá Cave based on \'delta\'D of n-alkanoic acids of 28 carbons, which are produced by terrestrial vegetation and macrophytes, and from \'\'delta\'POT.18\'O of speleothems. More positive (negative) isotope ratios indicate persistent dry (wet) climatic conditions during the MCA (LIA) there, due to a north (south) displacement of ITCZ. This climate system migrated toward the warmest ocean according to the correlation with Atlantic Multidecal Oscillation (AMO). The northern portion of the NEB (nNEB) presented different paleoclimate conditions when compared to the southern NEB portion (sNEB) during the LIA. LIA in sNEB was dry due to the displacement of the South Atlantic Convergence Zone (SACZ) to a southernmost position. Paleoenvironmental changes were attested by determining the age of clastic sequences filling cave conduits dated by OSL method and also by radiocarbon in bat guano. The deposition of terrigenous sediments in Urubu cave from 7 to 4 ky B.P. cave was chronologically associated with more humid climate indicated by low \'\'delta\'POT.8\'O values in speleothems. In addition, this period was marked by increased contribution of organic carbon from soil indicated by negative values of \'\'delta\'POT.13\'C of the same speleothems. An abrupt transition to dry climate was indicated by the end of clastic sedimentation at about 4.2 ky because interruption of underground river flow and complete erosion of soil surrounding the cave as indicated by abrupt enrichment of \'\'delta\'POT.13\'C values of speleothems, reaching values similar to the carbonate bedrock (~0 %o). These data demonstrated the relationship between the sedimentary filling of the Urubu Cave and the formation and soil erosion in the region. These predominant dry conditions during last three millenniums in the region were also important for preservation ofbat Guano deposits above terrigenous sediments. The chronological data of guano was also used to indicate two periods of high accumulation associated with intense occupation of caves by bat colonies between 1,730 and 677 years cal BP and 200 cal years BP until recently. During the MCA occurred a reduction in guano accumulation until a complete hiatus, because dry conditions did not favor bats survival. Guano deposit accumulated again only 200 years ago, when the population of bats restored with stabilization of relatively humid conditions.
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Weber, Michael [Verfasser]. "Reconstruction of past climate variability during Marine Isotope Stage 3 and the Holocene using speleothems: Special emphasis on the application of the Sr isotope system / Michael Weber." Mainz : Universitätsbibliothek Mainz, 2019. http://d-nb.info/1193943329/34.
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Labuhn, Inga. "Climate Variability in Southwest France During the Last 2000 Years : Proxy Calibration and Reconstruction of Drought Periods Based on Stable Isotope Records from Speleothems and Tree Rings." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01063541.
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The characterization of natural climate variability is important in order to understand the climate response to natural forcings and to identify anthropogenic influences. The aim of this thesis is to reconstruct climate changes in the southwest of France, a region which is characterised by recurrent drought periods, where high resolution proxy records of the last millennia were lacking.The reconstruction is based on multiple proxies from two continental archives: speleothems and tree rings. Their combination can make use of the strengths of each archive while compensating their weaknesses. There are two principal objectives: first, to gain a better understanding of the climatic and non-climatic influences on each proxy; and second, to reconstruct drought periods in the past.The oxygen isotopic composition (δ18O) of speleothem fluid inclusions and tree ring cellulose is controlled to a large extent by the δ18O of precipitation, which can serve as a tracer of the atmospheric circulation. In order to interpret these proxies in terms of climate, it is necessary to understand how the climate signal becomes recorded in the proxy, and which processes modify the original signal during the formation of the archive.Measurements of δ18O in precipitation, cave drip water, and fluid inclusions in modern speleothem samples from Villars Cave demonstrated that the isotopic composition of cave drip water corresponds to the pluri-annual average precipitation. The speleothem fluid inclusions, in turn, preserve the isotopic composition of the drip water. Based on this calibration, it is possible to reconstruct drip water isotope variability using fluid inclusions in a more than 2000 year old stalagmite, which has been dated by laminae counting, as well as U-Th and 14C measurements. Changes in the cave environment, e.g. the vegetation cover, are indicated by other proxies from the same stalagmite (stable isotopes in calcite and trace element concentrations), but these changes do not seem to impact the fluid inclusion δ18O significantly.The isotopic composition of tree ring cellulose from Quercus spp. in the study area is strongly influenced by climate conditions during the summer. However, non-climatic influences on the isotopic composition of cellulose are identified. They are linked to the age of the trees and to site hydrology, and must be accounted for in the sampling and analytical procedures. Crossdated cores from living trees and timber wood in historic buildings near Angoulême are used to build an annually resolved chronology of cellulose δ18O. Significant correlations with meteorological data enable a calibration and a reconstruction of drought periods since 1360 AD.Lastly, this thesis explores a novel approach of integrating oxygen isotope records from speleothem fluid inclusions and tree ring cellulose from closely located sites to reconstruct both high- and low-frequency variability of droughts in the past.
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DeLong, Kristine Lee. "Paleoclimatic reconstruction and evaluation of sub-centennial climate variability in the late Holocene using records from massive corals (New Caledonia), tree-rings (New Mexico) and speleothems (China)." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002726.
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CRUZ, ROSANA PETINATTI DA. "DEVELOPMENT OF A METHODOLOGY FOR CORALS AND SPELEOTHEMS DATING USING THE 230-TH/234-U METHOD, THROUGH CHROMATOGRAPHIC SEPARATION AND QUANTIFICATION BY ALPHA SPECTROMETRY AND FIA-ICP-MS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8544@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOO presente trabalho aborda as determinações de idades de espeleotemas e corais, usando o método de desequilíbrio da série urânio, mais especificamente, o método de deficiência de filhos daughter deficient DD, em particular o método 230Th/234U. Foram testadas diferentes metodologias empregando separação por extração cromatográfica e quantificação por espectrometria alfa e ICP-MS. Foram testados três procedimentos diferentes: separação em batelada empregando-se colunas com Tri-octil óxido de fosfina (TOPO) em silica- gel e a coluna TRU comercializada pela Eichrom(R), composta de octil-N,N,- isobutil carbamoil óxido de fosfina dissolvido em fosfato de tributila (TBP) e quantificação por espectrometria alfa; separação em batelada com os mesmos sistemas mas quantificação por ICP-MS e separação em linha (flow injection) com cartuchos de TRU e quantificação por ICP-MS. As metodologias desenvolvidas foram validadas empregando-se amostras de referência certificada, IAEA-327 (solo) tendo sido obtidas incertezas de 2% para o método empregando a separação em linha (flow injection) com cartuchos de TRU e quantificação por ICP-MS. As amostras de espeleotema analisadas foram coletadas no Carste de Lagoa Santa, MG, pelo grupo do Prof. Luis Piló (USP) e suas idades variaram de 15,2±2,2 kanos a >350 kanos. Estes valores estão na faixa dos valores encontrados na literatura para amostras de espeleotema coletadas pelo mesmo grupo na mesma região. A amostra de coral, coletada na Bacia de Campos (RJ) era da espécie Lophelia pertusa, foi subdividida segundo suas ramificações (primária, secundária e terciária) e o ramo principal foi datado em 9,4 ± 0,3 kanos.
This paper discusses the age determination of speleothems and corals using Uranium-series- imbalance method, more specifically the daughter deficient method - DD, particularly the 230Th/234U method. Different methodologies were tested using chromatographic extraction separation and quantification by alpha spectrometry and ICP-MS. Three different procedures were tested: batch separation using columns with Tri-N-Octylphosphine Oxide (TOPO) in silica gel and TRU column commercialized by Eichrom(R) composed of octyl-N,N,-isobutyl carbamoylphosphine oxide dissolved in tri-n-butyl phosphate (TBP) and with quantification by alpha spectrometry; batch separation with the same systems, but with quantification by ICP-MS; and flow injection with TRU cartridges and qualification by ICP-MS. The methodologies developed were verified using certified reference samples, IAEA-327 (soil) with 2% imprecision rate for the method using flow injection with TRU cartridges and qualification by ICP-MS. The speleothem samples analyzed were collected at Carste de Lagoa Santa, in the state of Minas Gerais, by Prof. Luis Piló`s (USP) group, and their ages varied from 15,2±2,2 kyears to >350 kyears. These numbers are within the range found in the literature for speleothem samples collected by the same group in the same region. The coral sample, collected at Bacia de Campos (RJ), and from the Lophelia pertusa species, was subdivided according to its ramifications (primary, secondary and tertiary), and the main ramification dated 9,4 ± 0,3 kyears.
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Deininger, Michael [Verfasser], and Augusto [Akademischer Betreuer] Mangini. "The European Holocene Climate from the Speleothem’s View : Investigating spatio-temporal coherent changes in European speleothem proxy time series / Michael Deininger ; Betreuer: Augusto Mangini." Heidelberg : Universitätsbibliothek Heidelberg, 2013. http://d-nb.info/1177810700/34.
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Whittaker, Thomas Edward. "High-Resolution Speleothem-Based Palaeoclimate Records From New Zealand Reveal Robust Teleconnection To North Atlantic During MIS 1-4." The University of Waikato, 2008. http://hdl.handle.net/10289/2575.
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Growth rates, δ18O and δ13C of five stalagmites from the west coasts of North and South Islands, New Zealand, provide records of millennial-scale climate variability over the last ~75 kyr. Thirty-five uranium-series ages were used to provide the chronology. δ18O of stalagmite calcite was influenced by changes in moisture source region, temperature and both δ18O and δ13C primarily display a negative relationship with rainfall. To assist interpretation of climatic signals δ18O profiles were adjusted for the ice-volume effect. Changes in these proxies reflect changes in the strength of the circumpolar westerly circulation and the frequency of southwesterly flow across New Zealand. MIS 4 was a period of wet and cool climate lasting from 67.7 to 61.3 kyr B.P., expressed in the stalagmites by an interval of strongly negative isotope ratios and increased growth rate. This contrasts with less negative δ18O and δ13C, and slow growth, interpreted as dry and cold climate, during much of MIS 2. This difference between MIS 2 and MIS 4 provides an explanation for why glacial moraines in the Southern Alps of MIS 4 age lie beyond those deposited during the last glacial maximum (MIS 2). Heinrich events, with the exception of H0 (the Younger Dryas), are interpreted from high-resolution South Island stalagmite HW05-3, from Hollywood Cave, West Coast, as times of wetter and cooler climate. Minima in δ18O and δ13C (wet periods) occurred at 67.7-61.0, 56-55, 50.5-47.5, 40-39, 30.5-29, 25.5-24.3 and 16.1-15. kyr B.P. matching Heinrich events H6-H1 (including H5a) respectively. This demonstrates a robust teleconnection between events in the North Atlantic and New Zealand climate. Minima in δ18O also occurred at similar times in less well-dated North Island stalagmite RK05-3 from Ruakuri Cave, Waitomo. Speleothems from low-latitudes have revealed that Heinrich events forced southerly displacement of the Intertropical Convergence Zone. This caused steepening of the temperature gradient across mid-southern latitudes, increased westerly circulation and resulted in wet conditions on the west coast of both islands. Immediately following H1 in the HW05-3 stable isotope profiles is another excursion to more negative isotopic values, suggesting wet and cold climate, lasting from 14.6 to 13.0 kyr B.P. Such a climate on the West Coast at this time has been previously suggested from glacier advance (e.g. Waiho Loop moraine) and decreased abundance of tall trees on the landscape. This event occurred too early to be a response to H0, but is synchronous with a return to cool climate in Antarctica. Thus West Coast climate appears to have been sensitive to changes in Antarctica as well as the North Atlantic. Isotopic minima (wet and cool climate) in South Island stalagmite GT05-5, which formed during the Holocene, first occurred 4.6 kyr B.P. This began a series of four oscillations in isotope ratios, the last terminating when the stalagmite was collected (2006). Onset of these oscillations is associated with initiation of ice advance in the Southern Alps, and beginning of the Neoglacial. The last oscillation displays enriched isotope ratios lasting from 1.2 to 0.8 kyr B.P. succeeded by depleted ratios lasting until 0.15 kyr B.P., mirroring the Medieval Climate Optimum and Little Ice Age, respectively, of European palaeoclimate records.
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Ruan, Jiaoyang. "Characterization of Holocene climate variability in the west of Europe and Mediterranean basin using high-resolution stalagmite records." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS223.
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Déchiffrer le climat de l’Holocène est la base d’une meilleure compréhension du climat moderne. En effet, à cette époque le climat en Europe est très complexe est montre de fortes variations spatiales et il reste beaucoup à faire pour améliorer la couverture géographique d’enregistrements bien datés et de haute résolution. En tant qu’archives paléoclimatiques, les spéléothèmes ont de larges avantages concernant leur chronologie et leur résolution temporelle et peuvent aider à combler cette lacune. Dans cette thèse, des stalagmites holocènes ont été sélectionnées selon un transect N-S entre les latitudes 35° et 65°N à l’ouest de l’Europe et du bassin méditerranéen (de la Suède à l’Algérie). Elles ont été datées densément par U-Th et échantillonnées à haute résolution pour analyser leur composition isotopique et géochimique. Le climat de l’Holocène a été déduit des analyses isotopiques de la calcite (δ¹³C, δ¹⁸O) et du rapport Mg/Ca. Combinées avec les données existantes et avec les simulations numériques des modèles, ces nouvelles données ont permis d’émettre des hypothèses sur les processus dynamiques contrôlant les changement climatiques régionaux comme les divers modes impliqués dans la circulation océanique et atmosphérique. Sur un site archéologique particulier, le lien climat/activités humaines a aussi pu être étudié. Les principaux résultats de cette thèse sont : 1) les enregistrements en δ¹⁸O, δ¹³C et Mg/Ca d’une stalagmite de la grotte de Villars (sud-ouest de la France), ont révélé une variabilité décennale à multimillénaire du climat au cours des derniers 14200 ans ainsi que les preuves d’une déforestation il y a environ 1000 ans ; 2) deux stalagmites provenant de la grotte de Villars au sud-ouest de la France et de la grotte Korallgrottan au nord-ouest de la Suède ont enregistré de façon remarquable l’événement climatique du 8.2 ka et les différentes étapes qui le composent montrant des différences régionales de température et d’humidité entre les deux sites. Celles-ci sont associées avec une interruption suivie d’une réorganisation de la circulation océanique et atmosphérique ; 3) les enregistrements en δ¹⁸O et en δ¹³C de deux stalagmites de la grotte de Villars suggèrent aussi l’existence d’une période humide multi-centennale il y a ~7200-7600 liée éventuellement à la fonte de la dernière portion de la calotte de la Laurentide ; 4) les isotopes stables (δ¹⁸O, δ¹³C) d’une stalagmite de la grotte du Père-Noël située au sud-est de la Belgique, révèle de larges variations hydro climatiques entre 10500 et 4200 ans. En particulier, une période sèche multi-centennale est mise en évidence il y a ~5600-6000 ans probablement liée à un changement des vents d’ouest ; 5) au nord de l’Algérie, dans la grotte de Gueldaman, plusieurs stalagmites ont montré, par leur δ¹³C et leur δ¹⁸O, l’impact d’une période sèche sur l’occupation humaine et finalement l’abandon du site par les hommes préhistoriques il y a ~4200 ansDeciphering Holocene climate is the basis to understand modern climate change. The Holocene climate of Europe is highly complex and shows large spatial differences; much is to be done to improve the spatial coverage of well-dated, high resolution climate records. Stalagmite as paleoclimate archive has large advantages in its chronology and their temporal resolution and thus can help in answering this question. In this thesis, stalagmites were collected, broadly along a meridional transect from 35 to 65°N, in the west of Europe and Mediterranean basin (from Sweden to Algeria). They were densely dated by the U-Th method and their isotopic and geochemical compositions were analyzed at high spatial resolutions. The Holocene climate was inferred from the stalagmite δ¹³C, δ¹⁸ and Mg/Ca time series. Combining with existent data and model simulations the collected new data was used to understand dynamic processes involved in driving regional change, such as varying modes of ocean and atmospheric circulation. Uniquely, the possible links between the changes of past climate conditions and human activities at an archeological site were examined, too. The main results of this thesis are summarized as: (1) The δ¹⁸O, δ¹³C and Mg/Ca records of a stalagmite from Villars Cave, Southwestern France document a series of decadal to multi-millennial climatic variations over the last 14200 years as well as deforestation ~1000 years ago; (2) The precisely-dated, sub-decadal δ¹⁸O, δ¹³C and Mg/Ca records of stalagmites from Villars Cave, SW-France, and Korallgrottan Cave, NW-Sweden, reveal multiple stage climatic variations in relation to the 8200 year event. Reconstructed variations in both temperature and humidity exhibit different patterns at the two sites, respectively, in the south and north of Europe, which can be associated with the interruption and reorganization of ocean-atmospheric circulation; (3) The δ¹⁸O and δ¹³C records of two stalagmites from Villars Cave suggest multi-century wetness ~7200-7600 years ago which possibly linked to the demise of last portion of Laurentide Ice Sheet; (4) The δ¹⁸O and δ¹³C records of a stalagmite from Pere Noël Cave, Southeastern Belgium reveal large decadal to millennial hydroclimate variations between 10500 and 4200 years ago. Particularly, multi-century enhanced aridity occurred ~5600-6000 years ago which probably had attributed to the changes in regional atmospheric circulation and the westerly jet; (5) The δ¹³C and δ¹⁸O records of two Mid-Holocene stalagmites from Gueldaman GLD1 Cave, Northern Algeria provide evidence of a prolonged drought ~4200 years ago in Western Mediterranean basin. The drought coincides with, and therefore may have contributed to, an abandonment of ancient human occupation of the cave
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Dredge, Jonathan. "Aerosol contributions to speleothem geochemistry." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5136/.
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There is developing interest in cave aerosols due to the increasing awareness of their impacts on the cave environment and speleothems. This study presents the first multidisciplinary investigation into cave aerosols and their contribution to speleothem geochemistry. Modern monitoring of suspended aerosol concentrations, CO2 and temperature in Gough’s Cave, Cheddar Gorge have presented a strong relationship with cave ventilation processes. Temporal variations of aerosol levels have demonstrated the ability of aerosol monitoring to record seasonal ventilation shifts, beyond anthropogenic influences. When used in combination with more established monitoring methods, suspended aerosol monitoring is a beneficial addition to cave environmental studies Theoretical modelling and calculations based on modern aerosol monitoring have established that aerosol contributions are highly variable. Aerosol contributions are of greatest significance under slow growth or hiatus scenarios and high aerosol deposition scenarios. Marine and terrestrial aerosol contributions have been quantified in a flowstone core from New St Michaels Cave, Gibraltar. Additionally, bio-aerosol deposits and bacterial colonisation have been identified as a potential source of trace element bioaccumulation and flowstone coloration in Yarrangobilly Caves, Australia.
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Baker, Andy. "Speleothem growth rate and palaeoclimate." Thesis, University of Bristol, 1993. http://hdl.handle.net/1983/a592ea03-cfe9-4b3d-aeec-8937286065ff.
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An initial study of the palaeoclimate signal contained within speleothem growth was undertaken by' investigating regional variations in speleothem Qrowth frequency. It was demonstrated that about 500 analyses in such a regional compilation were necessary to generate a statistically significant curve which did not suffer from sample bias. However, few such regions are likely to have such a larQe data set. That from north west Europe did provide a useful palaeoclimate record, giving evidence of multiple interstadial events within isotope stage 3, and a significantly low level of growth within stage Sa. An investigation was undertaken into the palaeoclimate signal contained in variations of speleothem growth rate, based on the theory derived by Dreybrodt (1981) and Buhmann and Dreybrodt (1985) from calcite precipitation kinetics. It was demonstrated that growth rate increases with increasing calcium ion concentration, temperature and water flux (drip rate for stalagmites, water film thickness for flowstones and seasonal variations in water availability for both speleothems); turbulent flow conditions and cave air pC02, which theoretically affect growth rate, were demonstrated to be Insi9nificant. If water flux, calcium concentration and temperature all increase with improving Climate, growth rate increases may reflect climatic improvement. In particular, it was demonstrated that stalagmites should be most sensitive to changes in calcium concentrations, temperature, and seasonal shut-off of the water feed, whilst flowstones would also be sensitive to changes in water film thickness. Theoretical growth rates were tested for recently forming speleothems in excavated caves and mines. For these, minimum growth rates were determined by knowing the date of excavation of the cave or mine, and the growth rate determining variables were measured over the course of a year. It was demonstrated that the theory accurately predicted growth rates for both stalagmites and flowstones within the 20' errors based on variations in calcium ion concentration and water film thickness. However, flowstones generally grew slower than that predicted by the theory, due to the seasonal shut-off of the water supply feeding these samples. For flowstones at Kent's Cavem, growth rate was observed to Increase with Increasing water availability, for stalagmites at Lower Cave, growth rate was shown to increase with increaSing drip rate. Assuming a good prediction of growth rate by the theory, applications to Quatemary speleothems were undertaken to determine past calcium ion concentration, temperature and water flux. Growth rates were determined by thermal ionisation mass spectrometric uraniumseries dating. The growth rate of one Holocene sample from Sutherland demonstrated that variations in growth rate over the last 7 ka did not depend on temperature variations, but either to changes in calcium concentrations due to vegetation change or a non-linear response to changes in water flow. Growth rates were also determined for two flowstones from Yorkshire which had grown over the last 200 ka. However, the very fast growth rates in these samples prevented a precise record from being obtained. Mass spectrometric dating also provided a record of the timing of growth commencement and cessation. This was shown to be more complex than previously considered; in particular the Holocene growth of the Sutherland stalagmite commenced 5 ka after glacier retreat in the region, the Yorkshire flowstone from Lancaster Hole had seven growth phases, each for only 1-3 ka, five of which correlated with solar insolation maxima. In contrast, another flowstone from Stump' Cross in Yorkshire was shown to grow in both interglacial, interstadial and glacial periods of the last 200 ka. An investigation was made into the use of 13C/1'C,(t>nM to determine the type of plant community at the time of speleothem formation, and whether a non-biogenic source of CO2 was present. 13C analyses of the Stump Cross flowstone gave elevated 13C not explicable by the plant communities present, nor were high enough to have a non-biogenic source. Further investigations are needed, but this evidence suggests caution in interpreting 13C records for flowstones. An annual signal of growth rate and growth rate variability was obtained from ultra-violet microscopic analysiS of luminescent banding within speleothems. Banding was demonstrated to be annual by mass spectrometric uranium-series dating, but was only preserved In 10% of a" samples. Variability of growth rate for the Holocene Sutherland stalagmite was compared to the theoretical annual variability of growth rate derived from annual variations in the growth rate determining variables observed today, and a good agreement was observed. Furthermore, for one period of growth, a 4-5 year period of rapid growth rate was demonstrated to correlate with the Hekla 3volcanic eruption in Iceland.
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Codispoti, Julie E. "Speleothem Genesis in Ohio Caverns: How Erosion of Overlying Strata Resulted in Different Speleothem Characteristics." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1299678130.
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